The present invention relates to an image forming apparatus which is preferably applied to an image processing apparatus such as a copying machine, a printer and a facsimile machine. To be more precise, the invention relates to an apparatus wherein a 3-way interface means is connected to an image memory and data bus which is split into two, and after control instruction is given to the interface means, input and output of an image acquisition means and an image reproduction means are controlled on a time series basis by the control instruction independently of the control means so that the control means can execute another data processing.
Recently, a digital copying machine which forms an image based on image data acquired from a document image has been put to practical use. In the copying machine of this type, image information of a document is read by a scanner or the like, and image information of the document is stored temporarily in an image memory. Then, the image information stored in the image memory is subjected to image processing such as image reduction, image enlargement and rotation, to meet a user's demand. Due to this, an image of the document can be printed on a prescribed transfer sheet, based on the image data which have been subjected to image processing.
A digital copying machine of this kind, on the other hand, is equipped with a memory with large capacity for storing image information of a document temporarily, and it needs a technology of efficient data transmission for the image information.
FIG. 7 is a block diagram showing an example of the structure of image forming apparatus 500 of a conventional type employing an image memory of this kind. This image forming apparatus 500 is equipped with CPU bus 1 shown in FIG. 7. The CPU bus 1 is connected to system control means 2, image memory 3, direct memory access controller (hereinafter referred to as DMAC) 4, image acquisition means 5 and image reproduction means 6.
The system control means 2 connected to CPU bus 1 has therein CPU2a, ROM2b, RAM2c and user interface section 2d. CPU2a is an IC which conducts overall control of the image forming apparatus 500, and its control program is stored in ROM2b. RAM2c is a memory used temporarily when CPU2a conducts operation, and it is needed for execution of control program.
For example, when control instruction such as a startup directive is outputted to image acquisition means 5 or image reproduction means 6, the control instruction is written in RAM2c by CPU2a, and after that, when an end of writing of image data is notified, those corresponding to the control instruction are verified.
User interface section 2d is one which is needed for interface between the present apparatus and a user, and the instruction of the user interface section makes CPU2a to execute prescribed data processing. Image memory 3 connected to CPU bus 1 is a memory with a relatively large capacity corresponding to plural pages, and it also stores code data by conducting coding processing, though this is not shown. DMAC4 is one which executes data transmission between devices without interposition of CPU2a, and compared with CPU2a, it can transmit data at higher speed.
Image acquisition means 5 connected to the CPU bus 1 has therein scanner-use interface 5a, scanner section 5b and page memory 5c. The scanner-use interface 5a conducts control for driving of scanner section 5b and control for writing and reading of image data (DATA) in page memory 5c. The page memory 5c is a memory for storing image data in quantity equivalent to one page coming from scanner section 5b, and it is needed for adjustment of data transmission speed between the scanner section 5b and CPU2a and for improving use efficiency for CPU bus 1. Since the page memory 5c is provided to adapt with the speed of the scanner, the page memory 5c needs not have the capacity for full or all pages.
Further, image reproduction means 6 connected to CPU bus 1 has therein printer-use interface 6a, page memory 6b and printer section 6c. The printer-use interface 6a conducts control for driving of printer section 6c and control for writing and reading of image data in page memory 6b. The page memory 6b is a memory for storing data to be written in printer section 6c in quantity equivalent to one page, and it is needed for adjustment of data transmission speed between the printer 6c and CPU2a and for improving use efficiency for CPU bus 1. As same as the case for the scanner, the page memory Sc needs not have the capacity for full or all pages.
Next, operations of the image forming apparatus 500 will be explained. First, copying operations for a single document will be explained. First of all, when instruction for one page copy is received from user interface section 2d, scanner driving is instructed from CPU2a to image acquisition means 5. In the scanner-use interface 5a which has received that instruction, the scanner section 5b is driven and image data of a document is acquired from scanner section 5b, and that image data are stored in page memory 5c in succession. When image data equivalent to one page are stored in page memory 5c, the scanner-use interface 5a notifies an end of image data reading to CPU2a.
CPU2a which has received the notification gives to DMAC4 the instruction for transmitting image data from scanner-use interface 5a to printer-use interface 6a. Then, image data equivalent to one page are transmitted from scanner-use page memory 5c to printer-use page memory 6b. When this transmission of image data for one page has been finished, an end of transmission is notified from DMAC4 to CPU2a. Then, printer driving is instructed from CPU2a which has received the aforesaid notification to image reproduction means 6. Then, image data are read from page memory 6b by printer-use interface 6a which has received the aforesaid instruction, and the image data are outputted to printer section 6c. On the printer section 6c, it is possible to copy an image of a document on a transfer sheet or the like based on image data for one page.
Next, operations for making plural sets of copies for plural documents will be explained. First, scanner driving is instructed to image acquisition means by CPU2a which has received the instruction from user interface section 2d. On the scanner-use interface 5a which has received the instruction, when image data equivalent to one page acquired by scanner section 5b have been stored in page memory 5c, an end of reading of image data equivalent to one page is notified to CPU2a from scanner-use interface 5a. Then, data transmission is instructed to DMAC4 by CPU2a which has received the notification, thereby, image data stored in page memory 5c are transmitted to image memory 3.
A series of aforesaid operations are repeated for the number of times equivalent to the number of documents, and all image data are stored in image memory 3. After that, image data thus stored are transmitted to printer-use interface 6a by the instruction of CPU2a. In this case, when image data equivalent to one page are stored by DMAC4 in printer-use page memory 6d from image memory 3, printer startup is instructed to printer-use interface 6a from CPU2a.
When image data equivalent to one page are outputted to printer section 6c by printer-use interface 6a which has received the instruction stated above, an end of printing is notified to CPU2a. Then, transmission of image data on the succeeding page is instructed to DMAC4 from CPU2a which has received the notification, whereby printing is started.
When a series of aforesaid operations are repeated for the number of times equivalent to the number of documents, copies for the first set are finished. Since plural sets of copies are instructed to CPU2a in this example, an instruction for transferring image data on the first page again to printer-use interface 6a from image memory 3 is given to DMAC4. After this, the same operations are repeated for the number of times equivalent to the prescribed number of sets, whereby copies of plural sets can be made.
In the case of image forming apparatus 500 of a conventional type, CPU2a, image memory 3, image acquisition means 5 and image reproduction means 6 are connected to one CPU bus 1, and when making copies of plural sets for plural documents, in particular, CPU bus 1 is arranged to be owned exclusively between image memory 3 and scanner-use interface 5a or between image memory 3 and printer-use interface 6a.
Therefore, there is a problem that CPU (hereinafter referred to as control means) 2a can not execute another data processing by the use of CPU bus 1, while image acquisition means 5 and image reproduction means 6 are using CPU bus 1 in accordance with the control instruction, after the control instruction is given to scanner-use interface 5a and printer-use interface (hereinafter referred to as interface means) 6a.
Therefore, the invention has solved the problems stated above, and its first object is to provide an image forming apparatus wherein a control means can execute another data processing by using another data bus, even when data bus is owned exclusively by an image acquisition means or an image reproduction means in accordance with a control instruction, after the control instruction is given to an interface means.
In the case of image forming apparatus 500 of a conventional type, there is a demand for a data processing apparatus wherein printer and facsimile functions are combined with a copying function by adding a communication means to the main apparatus. For this demand, image memory 3 is required to be used efficiently for conducting memory communication and broadcast. However, in the conventional type, image memory 3, DMCA4, image acquisition means 5 and image reproduction means 6 are connected to one CPU bus 1, and each of the means 5 and 6 is connected to page memories 5c and 6b.
Therefore, scanner-use and printer-use page memories 5c and 6b are not used except for operations of scanner section 5c and printer section 6c, which causes a problem of system structure that efficiency of using a memory is low. Incidentally, page memories 5c and 6b have capacity to record image data for the largest document size (for example, A3 size). Due to this, when copying a document whose size is smaller than A3 size, a memory area which is not used is caused, and efficiency of using a memory is lowered accordingly.
When making plural sets of copies for plural sheets of documents, namely, when making plural sets of copies simultaneously while printing out the first document after reading image data on one page, it is necessary to transfer image data to both of image memory 3 and printer-use page memory 6b from scanner-use page memory 5c, using DMAC4. Therefore, image data need to be split into two groups each being transmitted separately, which makes the transmission time to be about two times the data transmission time for a single document.
Further, there is an occasion where image data on the following page are overwritten accidentally on image data on the preceding page by DMAC4, because a transmission speed of DMAC4 connected to CPU bus 1 is changed by occupancy rate for CPU2a bus. This takes place when reading of image data on the following page is started before image data equivalent to one page are all transmitted from page memory 5a to image memory 3, when the transmission speed of DMAC4 is lowered by the change of occupancy rate for CPU2a bus.
In the same way, when the instruction for startup of the printer is made before image data equivalent to one page are stored in page memory 6b, there is an occasion where underflow of image data is caused and an upper portion of a document is not copied. To avoid this condition, when DMAC (hereinafter referred to as external equipment) 4 is caused to have priority to CPU2a to posses CPU bus 1 exclusively, there are caused problems that the processing speed of CPU2a is lowered, and it is difficult for CPU (hereinafter referred to as external equipment) 2a to execute facsimile processing wherein CPU bus (hereinafter referred to as data bus) 1 and image memory (hereinafter referred to as memory for data) 3 are used.
The invention has solved the problems stated above, and its second object is to provide a data processing apparatus and a system constructing method wherein even when an external equipment on one side possesses data bus exclusively, an external equipment on the other side can execute another data processing by using another data bus, and memories for data can be used commonly on a series of time basis by external equipment each being connected to each data bus.
In the case of image forming apparatus 500 of a conventional type, when the control instruction such as a startup instruction is outputted by CPU2a to scanner-use interface Sa or printer-use interface 6a, and then an end of writing and reading of image data is notified, there sometimes is an occasion wherein there is taken a method to check whether the end of writing and reading is for the aforesaid control instruction or not. Therefore, it is necessary to write the control instruction in RAM2c in advance and to keep it.
Therefore, for the period from outputting of a control instruction such as the startup instruction to scanner-use interface 5a or printer-use interface 6a to notifying of the end of the control instruction, it is necessary to confirm constantly whether the control instruction is recorded in RAM2c or not. Due to this, flow processing for control of input and output for scanner-use interface 5a and printer-use interface 6a is needed, and load of data processing for CPU (hereinafter referred to as a control apparatus) 2a is increased, which is a problem.
The invention has solved the problems stated above, and its third object is to provide an interface apparatus and a data processing system wherein load of data processing for the control apparatus in system superiority can be reduced in terms of data transmission.